1. Field of the Invention
The present invention relates to a motor drive controller and a method for controlling a motor.
2. Description of the Related Art
In paragraph 0030 of JP-A-H06(1994)-245590, it is described that “noise generated from a pulse motor can be greatly reduced by periodically modulating a motor driving frequency in a constant speed rotation period.”
In paragraph 0006 of JP-A-H06(1994)-245590, it is described that “when a pulse motor is driven at a steady speed (fo), the pulse motor is driven by superimposing a signal with a modulation width (Δf) varying in a period (1/fs) at the steady speed (fo).” In paragraphs 0022 to 0027 of JP-A-H06(1994)-245590, it is described that “setting ranges of the period (1/fs) and the modulation width (Δf) in which a good noise reduction effect is obtained.”
When a stepping motor has a resonant frequency at a predetermined drive speed and the motor is driven at a speed close to the resonant frequency, there were problems that large vibration ripples occur based on a frequency modulation and abnormal noise (beat noise) occurs. There is also a problem that torque ripples occur due to the frequency modulation.